During road construction, storm drains (also known as catch basins) and sewer inlets are disposed at various points along the road to evacuate excess water and/or debris that may accumulate. Such accumulation can occur for example during rainfall.
The storm drains (or catch basins) are connected to a sewerage system which is a network of pipes, pumps, and force mains for the collection of wastewater, or sewage, from the community. Typically, storm drains use a separate and distinct sewerage network from sanitary sewer systems for human waste. Sometimes a combined system provides only one network for all types of sewage and excess water or debris.
In order to evacuate the excess water and debris toward the sewerage system, the storm drain includes an inlet disposed on the road surface. Two main types of inlets exist: the side inlet and the grated inlet. The sewerage typically ends in an outlet for the water which is a single large exit at the point of discharge. The separation of storm sewers from sanitary sewers helps to prevent sewage treatment plants becoming overwhelmed by infiltration/inflow during a rainstorm, which can result in untreated sewage being discharged into the environment.
The grated inlets prevent pedestrians, vehicles and large objects from falling into the storm drain. The design of the grate bars facilitates a flow of water towards the inside of the drain. Storm drains provided in streets and parking areas must be strong enough to support the weight of the vehicles. Some of the heavier sediment and small objects or debris may enter the grated inlet and settle in the catchbasin below the inlet. A frame is provided for the catchbasin or catch pit and the grate covers the open top of the frame of the catchbasin.
The grate is usually made of a ductile iron material and is simply fit flush with the open top of the frame. The grate has to be able to sustain different types of loads and different weather conditions. When a road is deviated from its usual path, the frame and grate may experience a traffic greater than it is normally exposed to. In some cases, the traffic forces the grate out of the frame, leaving the conduit or pipe head exposed, and thereby revealing a hole in the road. Having the conduit head exposed can become problematic for the road users.
In order to prevent the grate from detaching from the frame, some have solidified the grate to the frame. While this may allow the grate to stay connected to the frame, it prevents later access to the conduit for maintenance of the sewerage system.
Others have installed weights hanging downward from the grate in the conduit to weight the grate down toward the frame. However, these weights make it difficult for the grate to be removed during maintenance.